For decades, scientists have been fascinated by this secret magnetic history of the Moon. Recent studies show that the Moon definitely once had a magnetosphere. Today, it has no built-in magnetism whatsoever. Now, researchers are exploring the origins of this strange phenomenon. In particular, they are interested in the Moon’s core and its interactions with solar-generated magnetic fields.
The Moon’s core is quite small, which would go hand in hand with a weak magnetic field. Recent paleomagnetic estimates indicate that the Moon’s magnetic field strength was at least up to 1 μT. This is about fifty times weaker than the magnetic field of the Earth today. This major discrepancy casts doubt upon the hypothesis that the Moon had a much stronger magnetic field in its early history. What geological processes tromped across the landscape to create such a feature?
The Imbrium Basin and Its Significance
One of the most striking geological features on the Moon, the Imbrium basin on the near side. This enormous impact crater is located in a stunning location, dead center on the opposite side of the Moon. Researchers have been especially fascinated by this space. The basin’s formation is believed to be related to one of the largest impacts in lunar history, which could have played a crucial role in shaping the Moon’s magnetic character.
Scientists have long known that remnants of that strong magnetic field still exist. These residuals are evidence that the Moon was once subjected to a magnetic environment radically different from the desolation we see today. Research into high impact events such as the one that created the Imbrium basin exposes some fascinating links to lunar magnetism. Such an exploration would undoubtedly reveal new clues to untangle the Moon’s history and geological evolution.
“For several decades, there’s been sort of a conundrum over the moon’s magnetism—is it from impacts or is it from a dynamo?” – Rona Oran
Investigating Giant Impacts and Magnetic Field Amplification
In 2020, researchers Oran and Weiss conducted simulations of a giant impact on the Moon to test theories regarding its magnetic field. According to their findings, this impact would have created a large envelope of plasma. This plasma, in turn, interacted with the Moon’s weak intrinsic magnetic field to generate what’s known as an amplification or linchpin effect. This work would have been done very quickly, just about 40 minutes to run through from beginning to end.
Isaac Narrett, one of the research team’s graduate students, said there is still a lot to be discovered about lunar magnetism. He stated, “There are large parts of lunar magnetism that are still unexplained.” This recognition underlines the ongoing hurdles scientists face every day. More than that, they labored mightily to piece together the complicated celestial puzzle of Earth’s moon magnetic history.
The new simulations suggest that the giant impact scenario could be more than just a conjectured possibility. To test these hypotheses, researchers are working to corroborate them by pairing physical evidence from rock samples with computational models. Through this research they want to improve their understanding of how such impacts might affect magnetism on celestial bodies.
“It’s as if you throw a 52-card deck in the air, in a magnetic field, and each card has a compass needle,” – Benjamin Weiss
The Path Forward for Lunar Magnetism Research
Scientists are just as excited to prove their hypotheses about lunar magnetism wrong. They’ll directly sample pieces of the lunar rock record, looking for evidence of shock and intense magnetism. These kinds of exploratory efforts will be key in providing data that can support or counter prevailing theories about the Moon’s magnetic past.
As space agencies continue to plan future missions to the Moon, including manned missions, opportunities for direct analysis of lunar materials will increase. Each of these missions will provide us with priceless data not just on the nature of lunar magnetism, but on planetary processes at large.